A Super Bowl primer. Sunday's key? It's defense vs. defense

If you're a pro football fan, what do you look for Sunday in Super Bowl XXI between the New York Giants (16-2) and the Denver Broncos (13-5)? Well, one thing you don't look for is any major switch in the offensive and defensive strategy both teams rode safely through the National Football League's regular season and playoffs. This conclusion is prompted by nothing more complicated than the old ``if-it-ain't-broke,-don't-fix-it'' theory. Sure there will be subtle adjustments by both teams, but that's about all.

Right here it seems necessary to go to professional football's instant-clich'e rack to remind everyone that ``you score touchdowns with offense, but you win championships with defense.''

As for pride having much to do with winning a Super Bowl, Vince Lombardi settled that years ago when he said: ``Pride doesn't mean anything, because every team that gets this far has pride. If there is a secret to winning, it's picking the kind of player who performs well under pressure, who won't leave his game or his heart in the locker room.''

Here are the scouting reports:

The New York Giants have been a special team all year because of their HAM defense, meaning hostile, agile, and mobile. They not only come hard after the people with the ball, they come in groups.

Fancy? Forget it. They don't know what the term means. Only last year's Super Bowl champion Chicago Bears gave up fewer points (187 to 236 for the Giants) during the 1986 regular season, and most experts agree that the Bears played an easier schedule.

Offensively, New York has a somewhat mechanical quarterback in Phil Simms, who stays in the pocket of blockers which was designed for his protection, and who seldom tries for plays beyond his ability. While implying that Simms plays in a robot-like fashion may offend some Giants fans, the reference isn't meant to be derogatory. It is merely used to emphasize his consistency.

The Giants' running attack consists mostly of Joe Morris, who is also the safety valve for Simms when all his receivers are covered. But give fullback Maurice Carthon, who could probably block a tank, some credit for the way he opens holes for Morris.

The Denver Broncos are a big-play team offensively because of quarterback John Elway, who has the kind of radar vision that could probably locate a receiver in a pea-soup fog. Some people think Elway's long passes are heaved so far they must break some kind of federal aviation law.

Anyway, it's probably lights out for Denver if the Giants are able to get a net on Elway or his many receivers. But if John can scramble and still find his targets downfield, the Broncos have a chance.

While Denver's defense isn't as apt to knock people off the ball as often as New York's does, the players who make it work (including the special-team members who cover punts and kickoffs) are much admired by opponents.

There are a lot of keys needed to lock up a rival offense, but none bigger on the Broncos than linebacker Karl Mecklenburg. If there is a better linebacker in the American Conference right now, he's masquerading as two people.

Although Karl's teammates call him the Snow Goose because of his blond hair, he goes after a running back like a panther. The Broncos also have an umbrella-like defensive secondary that provides excellent coverage and disguises things so well that few opposing quarterbacks can find any seams in it. New York coach Bill Parcells is the methodical type with a personality that soothes rather than burns. Give him a knot of problems and he'll evaluate them, break them down so they don't look so big, and solve them. His rapport with players has been another strong point, symbolized by the playful ceremonial dousing he received from veteran linebacker Harry Carson after each victory this season.

There is nothing flamboyant about Parcells's offense. It uses just the standard plays, with options. They work because of nearly perfect team execution.

Bill's defense is the same way - standard stuff that contains the run and takes away the bomb.

Thanks to the wise drafting of general manager George Young in recent years, Parcells is also in the happy position of having reserves who are very close in talent to his starters.

Like Lombardi's old Green Bay Packers, this Giant team excels in fundamental skills, such as blocking and tackling, and it makes its opponents pay a high price for every piece of football real estate.

Denver coach Dan Reeves has benefited from his years as a young National Football League assistant coach. Few assistants in recent years have had a more thorough indoctrination into what it is like to coach pro football.

Before coming to Denver, Reeves spent eight years working with Tom Landry, coach of the Dallas Cowboys. Dan, whose last job with Dallas was as the offensive coordinator, has the same computerlike thinking process that Landry has employed so well for so many years, plus the same flair for defense.

Reeves would probably never admit it, but it is not uncommon for the Broncos to resort to 20 different pass coverages and 10 different defensive fronts. While this is hard on Dan's own people, it is even tougher on opponents. If Reeves's defensive sets confuse the sophisticated Giants, however, it will be the first time it has been done to them all season. Final glances: The Giants are likely to immediately test the Broncos with their running game, hoping to control the football for long periods of time by grinding out first downs.

The Broncos will probably open things up right away. Elway may come out throwing - not bombs, but quick sideline passes.

Although the last three Super Bowl champions (the Los Angeles Raiders, San Francisco 49ers, and Chicago Bears) have scored 38, 38, and 46 points, respectively, such high numbers probably won't be reached on Sunday. When the teams met in the New Jersey Meadowlands during the regular season, the Giants won, 19-16.

Whenever the Giants get a decent lead, Parcells likes to have his offense stay on the ground and eat up the clock. The Broncos, on the other hand, because of their Mickey Mouse running game, would probably have to risk putting the ball in the air to maintain possession for any length of time.

On paper, this game doesn't offer one of the more compelling Super Bowl match-ups. But while the Giants are clear-cut favorites, Elway may have the ability to keep things closer than expected, though few people think even he can make enough difference to pull the game out for the Broncos.

How - and why - did the Super Bowl get started? See today's sports page.